Case Study Pueblo Chemical Depot RCRA Facility Investigations for SWMUs 13 & 12 “A Tale of Two SWMUs” 3 April 2019
Site and SWMU Locations SWMU 13 SWMU 12 Location: Approximately 25 miles east of Pueblo, CO Red Line is the PCD Boundary
Project Background Key Points: • • Both sites suspected historical chemical warfare materiel (CWM) destruction / disposal areas • SWMU 13 is approximately 1 acre and SWMU 12 is approximately 6 acres • SWMUs are fenced with warning signage, on an active installation with limited access • Industrial re-use goal State Concurrence: Obtained for SWMU 13 • Pending for SWMU 12 ∆ Cost to Use the RMM vs. MEC HA: Not significant •
Overview of SWMU 13 • Fenced location approximately one acre in size on the eastern side of PCD. • Used for the destruction of intact and leaking chemical weapons from 1942 to 1946. • Confirmed destruction of HS-filled and L-filled M70 115-pound chemical bombs (mustard). • Investigation at SWMU 13 was a removal action defined as a 100% characterization of the disposal pits.
Overview of SWMU 12 • Fenced location, approximately 6 acres in size on the western side of Items Staged for Destruction PCD, selected for RFI/CMS • Location used for the destruction of defective chemical shells (including HD-filled) from 1953 to 1969 • Potential disposal of over 6,000 chemical projectiles or mortars, some explosively configured Typical Disposal Pit • Disposal included explosive detonation, chemical decontamination, and burning material with diesel fuel
Site Characterization SWMU 13 SWMU 12 • 100% DGM coverage • Collected DGM data data over suspected over suspected disposal pits disposal pits and delineated 8 • Excavated entire “anomalous areas” disposal area indicated to have • Exploratory trenches been disturbed or excavated at each impacted “anomalous area” down to native soil • Confirmatory sampled and backfilled
RFI Results and Conclusions SWMU 13 – Deemed “clean” following removal action and additional testing • No MEC encountered/remaining – All CWM removed – No CA; No ABP/HTW/MC over standards – “Acceptable Risk” for Explosives using RMM – Accepted by CDPHE for No Further Action SWMU 12 – Strongly suspected to be contaminated – RFI investigation defined nature and extent • Presence of MEC and limited CA residue in munitions confirmed – No CA in soil; ABP below standards – HTW/MC exceeded standards – “Unacceptable Risk” for Explosives with RMM – Note: HTW/MC and possible CWM also of concern – Recommended for Corrective Measures Study
Positive Features of the RMM • Covers the familiar/traditional risk factors: – probability of MEC exposure – probability of detonation if encountered – consequence of detonation • More directly linked to the DQO setting process • Follows a logical progression through the hazard assessment process • Provides effective, consistent framework for focused communication and discussion with stakeholders
Challenge #1 - Interpreting Exposure Factors " Access Conditions (frequency of use) " in Matrix 1 and the " Likelihood of Encounter " in Matrix 2 are related but the linkage is unclear as currently represented • " Access Conditions " seem to address the degree of open or closed access to the site AND the frequency of site access/use • " Likelihood of Encounter ” seems to address the frequency of site access/use AND the nature of the activities that create the opportunity for contact Distinction/linkage between these two factors is easily blurred • Should the frequency of use/access be the dominant consideration in selecting an assignment for both factors?
Challenge #2 - Projecting Consequences Difficulty in assigning the " Severity Associated with Specific Munitions Items " factor in Matrix 2 • Choosing between “ Catastrophic/Critical” and “ Modest” assignments is not straightforward – Extent/severity of the impact of a detonation depends on the circumstance of the incident – Depends on factors such as: type/size of munition; manual or mechanical contact; adult or child; unintentional or “encouraged” interaction; and possibly other factors How conservative should one be when selecting an assignment for this factor when faced with unknowns?
Challenge #3 - Consistency with Other Assessments Maintaining consistency with concurrent risk assessments, MRSPP updates, or previous MEC HAs The frameworks have different stated purposes and incorporate different levels of • conservatism Each tool appears to be “similar” to many stakeholders who expect “similar” • results/findings Uncertainties arise when assigning factors • that address similar conditions within the various frameworks – MEC Presence/Absence – Land Use – Exposure Frequency and Duration Would the RMM scoring be different if completed separately from other assessments? Can/Should the RMM scoring be influenced by the results of other concurrent assessments?
Challenge #4 - What About CWM? • RMM was developed to assess explosive hazard, not the potential for direct contact or inhalation exposure to chemical agents (CAs) or agent breakdown products (ABPs) • Some RMM explosive hazard risk factors may also be relevant and applicable to CWM – Amount, Access Conditions, Likelihood to Impart Energy • Other RMM risk factors are not so relevant or transferable to CWM – Severity of a Detonation/Release, Sensitivity: Susceptibility to a Detonation/Release • The “Acceptable” and “Unacceptable” RMM Matrix 4 combinations were designed with MEC in mind • It is conceivable that an RMM-like tool could be developed for CWM, but the current RMM should not be used for that purpose
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